1. Field of the Invention
The present invention relates to exposure apparatuses, exposure methods, and device manufacturing methods, and more particularly to an exposure apparatus and an exposure method used in a lithography process to manufacture microdevices such as a semiconductor device, and a device manufacturing method using the exposure method.
2. Description of the Background Art
Conventionally, in a lithography process for manufacturing electron devices (microdevices) such as semiconductor devices (such as integrated circuits) and liquid crystal display devices, exposure apparatuses such as a projection exposure apparatus by a step-and-repeat method (a so-called stepper), or a projection exposure apparatus by a step-and-scan method (a so-called scanning stepper (which is also called a scanner) is mainly used.
In these types of exposure apparatuses, with finer device patterns due to higher integration of semiconductor devices, requirements for high overlay accuracy (alignment accuracy) is increasing. Therefore, requirements for higher accuracy is increasing, also in position measurement of substrates such as a wafer or a glass plate and the like on which a pattern is formed.
As an apparatus to meet such requirements, for example, in U.S. Patent Application Publication No. 2006/0227309, an exposure apparatus is proposed which is equipped with a position measurement system using a plurality of encoder type sensors (encoder heads) installed on a substrate table. In this exposure apparatus, the encoder head irradiates a measurement beam on a scale which is placed facing a substrate table, and measures the position of the substrate table by receiving a return beam from the scale.
However, in the exposure apparatus which is equipped with the position measurement system described in U.S. Patent Application Publication No. 2006/0227309, as for the actual operation, the encoder head facing the scale has to be switched from a plurality of encoder heads according to the position of the substrate table. Furthermore, when switching the encoder head which is to be used, continuity of the position measurement results of the substrate table also has to be secured.